Coolant Problems, Leak?
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Cadillac Seville / Cadillac Eldorado Forum Discussion, Coolant Problems, Leak? in Past Cadillac Vehicle Discussion; Ok, I've been having some issues with my 98 Eldorado ETC loosing coolant. I had a pressure test done and ...
  1. #1
    dave_noffsinger is offline Cadillac Owners Member
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    Question Coolant Problems, Leak?

    Ok, I've been having some issues with my 98 Eldorado ETC loosing coolant. I had a pressure test done and found a couple small leaks around the upper hose and one of the heater core hoses. I have replaced the upper and lower hoses as well as the heater hose. I went ahead and put in a new thermostat and gasket while I was in there. I'm not finding any other leaks nor are there any puddles or evidence of coolant on the garage floor.

    My wife drove the car for 2 days and said that the coolant warning came on. I checked it Tuesday night and it was low. Actually I ended up putting almost a full gallon in there. My wife said that she had to add coolant again this morning. It's loosing close to a gallon in about 100 miles.

    Since I can't seem to find the leak I'm wondering if there is something else I can check. Should I go ahead and do a compression test? Also, what's the stats on the compression for the N-Star anyway? I've read several threads on here about the water pump gasket leaking. I'm not seeing a leak but could there still be a problem with that?

    Any help would be greatly appreciated.

    Thanks,
    Dave

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  3. #2
    Zorb750 is offline Cadillac Owners Connoisseur
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    Re: Coolant Problems, Leak?

    Head gasket possible. Water pump gasket leak is easy to find, there will be white chalk like deposits on the bottom of the water pump housing. Scrape at it with a screwdriver and you will find out. Let it cool first so it would dry. A little's sometimes there. More than a tiny amount is bad. The new gasket will be a redesigned part. It will last longer and is less likely to leak. They are reusable BTW.

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Coolant Problems, Leak?

    If your water pump or the cover gasket were leaking a gallon per 100 miles, I suspect you'd see evidence of it.

    Compression test won't tell you anything. You need to do a cylinder pressure test. There is a big difference.

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    dave_noffsinger is offline Cadillac Owners Member
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    Re: Coolant Problems, Leak?

    Yeah, that's kind of what was puzzeling me I guess. I would have figured that with that much coolant missing I would have seen some kind of evidence of it somewhere. I didn't know if it was possible for some blockage of some sort to cause the coolant to back up into the resivor and out the overflow when she's driving it or something. At least I was hoping that it might be something like that vs a blown head gasket ya know.

    On that cylinder pressure test.... I saw another posting talking about taking an old spark plug and hollowing it out so that you could hook it up to a compressor and pump air into it. Just wondering exactly how it was done really. Do you just drill out the plug and put a hose around the top with a hose clamp? Just trying to figure out how I can do that and not get air leaks I suppose.

    Dave

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    Re: Coolant Problems, Leak?

    You need to grind off the rolled edge where the base meets the ceramic. Then you can break off the ceramic and gut it. Then you have to get a 1/8" pipe tap, tap the base and screw in a quick disconnect coupler for your air hose.

    My compression tester has a hose with threads on one side and a quick disconnect on the other. Much easier.

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    Dadillac's Avatar
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    Re: Coolant Problems, Leak?

    If, when the coolant reservoir was topped off after the reapirs, the system wasn't "burped", this situation will occur. It isn't actually losing coolant, it is just being replaced by the air still in the system. Check the coolant level again, after driving the car a few miles. It may not need anymore. If the level does drop again, then start investigating.

    Don

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    dave_noffsinger is offline Cadillac Owners Member
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    Re: Coolant Problems, Leak?

    Ok, thanks for the info guys. I'm going out there today to check on it. My wife said that on her way home last night she had the hood up and saw some coolant around the back of the resivor. I'm not sure if that's come out of the overflow tube or not. I did put a new cap on it recently so that should be good. I'm also wondering if anyone has had problems with a crack in the resivor as well. I figured I would pull it off to check and see. If I don't find anything simple I'm going to try to modify an old plug and do the cylinder test like you guys suggested.

    Thanks,
    Dave

  9. #8
    Zorb750 is offline Cadillac Owners Connoisseur
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    Re: Coolant Problems, Leak?

    Quote Originally Posted by Ranger
    You need to grind off the rolled edge where the base meets the ceramic. Then you can break off the ceramic and gut it. Then you have to get a 1/8" pipe tap, tap the base and screw in a quick disconnect coupler for your air hose.

    My compression tester has a hose with threads on one side and a quick disconnect on the other. Much easier.
    I agree with Ranger about the compression tester method. I bought one like it from a Meijer store for $39, and have seen it for around $20 more in Murray's and Auto Zone.

    Just make sure the valves are closed when you're testing a given cylinder. If air just flows freely and you hear it from "below" the exhaust's open. If you hear it from the top of the engine or your airbox, the intake's open. Exhaust will be more evident, because the throttle plate will block some airflow. (If in doubt, actuate the throttle body. If sound changes, it's intake)

    Quote Originally Posted by dave_noffsinger
    Ok, thanks for the info guys. I'm going out there today to check on it. My wife said that on her way home last night she had the hood up and saw some coolant around the back of the resivor. I'm not sure if that's come out of the overflow tube or not. I did put a new cap on it recently so that should be good. I'm also wondering if anyone has had problems with a crack in the resivor as well. I figured I would pull it off to check and see. If I don't find anything simple I'm going to try to modify an old plug and do the cylinder test like you guys suggested.
    Yes, surge tanks are known to crack. Start it, run it. When it's hot look for steam. Just don't open the cap! Steam billows a bit, but look at the currents with a flashlight. Do it in the dark if you can with no lights on in your garage (door open please!) or no floodlights in your driveway and the car headlights off. You'll see it if it's leaking externally that badly.

  10. #9
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Coolant Problems, Leak?

    Dried Dex-Cool will leave a white telltale residue. I had the purge line nipple on the surge tank crack on my '97 Deville. It was a hairline crack and was not visible unless the engine was running, and then just barely.

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